Should voting be mandatory in the United States?

There's a philosophical problem the pro side waves away. The secret ballot exists so nobody can coerce your vote: not your boss, not your spouse, not the state. Mandatory voting is the state coercing your participation. You can say 'but you can cast a blank ballot,' and that's true, but the state is still standing over your shoulder saying be in this booth. A right you get punished for not exercising is really a duty, and we should be honest that this proposal converts voting from one to the other.